Category page

You can look through the category page with its subcategories which contain tests. 
Also there is a hint on each test to see whole name of current test.
use collection

``` javascript
subcategories = {
  '1': [{"id": 2, "category_id": 1, "title": "Футбол"}, {"id": 3, "category_id": 1, "title": "Хокей"}],
  '4': [{"id": 5, "category_id": 4, "title": "Історія України"}, {"id": 6, "category_id": 4, "title": "Історія світу"}]
  //...
}
```